Burst mode cooling system

ABSTRACT

Disclosed are systems and methods of rapidly cooling thermal loads by providing a burst mode cooling system for rapid cooling. The burst mode cooling system may include a complex compound sorber configured to rapidly absorb ammonia.

BACKGROUND Field of the Invention

This disclosure relates generally to sorption refrigeration systemsusing sorbers and with complex compounds and a sorber gas that areconfigured to provide rapid cooling features. In particular, featuresfor a rapid pulldown of a thermal load, for example for flash freezingor cooling a fast-rising heat load.

Description of the Related Art

Adsorption/desorption or also referred to as absorption/desorptionreactions between polar gases and certain metal salts yield complexcompounds which are the basis for efficient refrigeration, thermalstorage, heat pump systems and power systems having high energy density.However, energy density, a measure of the quantity of polar gas adsorbedon the salt, which translates into the amount of work or energy whichcan be stored in a given amount of the complex compound, is only oneparameter to be considered in designing commercially attractive systems.

Of significance, if not greater importance, are the reaction ratesbetween the gas and the complex compound, which result in the time ittakes to adsorb and desorb a given amount of the gas into or from thecomplex compound. Increased or maximized reaction rates result inincreased or improved power that can be delivered by the system, i.e.,more energy delivered over a period of time, which translates into agreater heating, cooling or power capability of the system.

The reaction rates in these systems are partly a function of howefficiently the gas is distributed to the complex compound. Previoussystems have used porous ceramics or cloth to distribute gas to thecomplex compound. However, the ceramic distributors are fragile and canfracture easily, especially in non-stationary or vibratory environments.For example, ceramic distributors can have difficulty withstanding thevibrations caused by transportation in rough terrain. Cloth distributorshave also been found to have some downsides, particularly due to theirpropensity to clog after multiple cycles. This clogging can increase thepressure drop of the refrigerant in the systems and thereby reduce theperformance of the sorber and the absorption system.

SUMMARY

The embodiments disclosed herein each have several aspects no single oneof which is solely responsible for the disclosure's desirableattributes. Without limiting the scope of this disclosure, its moreprominent features will now be briefly discussed. After considering thisdiscussion, and particularly after reading the section entitled“Detailed Description of Certain Embodiments,” one will understand howthe features of the embodiments described herein provide advantages overexisting systems, devices and methods for distributing gas in complexcompound reactors.

One embodiment is a burst mode ammonia based cooling system thatincludes: at least one sorber comprising a complex compound sorbentconfigured to absorb and desorb ammonia; at least one heat sourcethermally connected to the at least one sorber; one or more condensersin fluid communication with the at least one sorber; one or more anevaporators in fluid communication with the at least one sorber; and aburst mode controller configured to activate a valve to provide a burstof heat absorption at the evaporator, where the absorption period of thecomplex compound is between 5 seconds and 300 seconds and the desorptionperiod is between 180 seconds and 15 minutes.

Another embodiment is a method in a complex compound sorber system ofburst mode cooling a thermal load. The method includes: detecting whento activate a burst mode cooling cycle; activating a valve that allowsammonia to flow into at least one sorber comprising a complex compoundsorbent, wherein the sorber is connected to an evaporator and theactivation provides a burst of heat absorption at the evaporator; andcontrolling the absorption period of the complex compound to between 5seconds and 300 seconds and the desorption period to between 180 secondsand 15 minutes.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present disclosure will becomemore fully apparent from the following description and appended claims,taken in conjunction with the accompanying drawings. Understanding thatthese drawings depict only several embodiments in accordance with thedisclosure and are not to be considered limiting of its scope, thedisclosure will be described with additional specificity and detailthrough use of the accompanying drawings. In the following detaileddescription, reference is made to the accompanying drawings, which forma part hereof. In the drawings, similar symbols typically identifysimilar components, unless context dictates otherwise. The illustrativeembodiments described in the detailed description, drawings, and claimsare not meant to be limiting. Other embodiments may be utilized, andother changes may be made, without departing from the spirit or scope ofthe subject matter presented here. It will be readily understood thatthe aspects of the present disclosure, as generally described herein,and illustrated in the figures, can be arranged, substituted, combined,and designed in a wide variety of different configurations, all of whichare explicitly contemplated and make part of this disclosure.

FIG. 1 is a line graph showing the absorption rate of ammonia onto CoCl₂over time and shows that the absorption rate at the lean end of thecoordination sphere, approximately the first up to about five minutes ofthe reaction, is much faster than outside the lean end of thecoordination sphere.

FIG. 2 is a line graph showing the absorption rate of ammonia onto SrCl₂over time and shows that the absorption rate at the lean end of thecoordination sphere, approximately the first up to about five minutes ofthe reaction, is much faster than outside the lean end of thecoordination sphere.

FIG. 3 is a schematic illustration of an embodiment of a burst modecooling system.

FIG. 4 is a schematic illustration of an embodiment of a sorber that ispart of the burst mode cooling system of FIG. 3.

FIG. 5 is a block diagram of an embodiment of a controller that is partof the burst mode cooling system of FIG. 3.

FIG. 6 is a flow diagram of an embodiment of a process for activating aburst cooling feature of the burst mode cooling system of FIG. 3.

DETAILED DESCRIPTION

Systems and methods are disclosed for rapidly cooling products, devicesor other heat loads. Such systems use an ammonia gas sorption systemlinked to an evaporator to rapidly cool the target product or device.Solid-gas sorption reactions, i.e., adsorption and desorption of the gason the solid, may be carried out under conditions and in an apparatusintended to yield high power densities. In one embodiment the adsorptionperiod and the desorption period are at different rates to maximize thepower density and rapid cooling characteristics of the sorber system.

In one example, the burst mode cooling system is part of a rapid coolingsystem for flash freezing products. In flash freezing, a product isbrought from one temperature to a second temperature below freezing in ashort period of time. In the food industry, flash freezing is performedto maintain the quality of the frozen food. Any other uses, where rapidcooling is desired, is contemplated within this application. Such casesinclude rapidly heating electronics and laser elements.

Because solid-gas sorption systems operate by adsorbing gas onto thesolid complex compounds and then driving the absorbed gas off thecomplex compound through heating, they may be run on a myriad of energytypes. For example, the system may be heated by fossil fuels, such asdiesel or JP-8, electricity, natural gas, solar thermal or any othertype of heating system that has enough thermal power to drive theammonia gas from the complex compound sorbent.

In order to provide the relatively fast absorption rates contemplated bythe burst mode cooling system, the system may use one specific complexcompound and refrigerant, such as phase change ammonia. In oneembodiment, the complex compound sorbent is CaCl₂, MgCl₂, CoCl₂, FeCl₂,SrBr₂, SrCl₂, CaBr₂ or MnCl₂ in combination with ammonia (NH₃) as therefrigerant. However, it should be realized that the complex compoundmay be selected from the following groups of salts:

(1) an alkaline earth metal chloride, bromide or chlorate salt,

(2) a metal chloride, bromide or chlorate salt in which the metal ischromium, manganese, iron, cobalt, nickel, cadmium, tantalum or rhenium,

(3) a double chloride salt selected from NH₄AlCl₄, NaAlCl₄, KAlCl₄,(NH₄)₂ZNCl₄, (NH₄)₃ZnCl₅, K₂ZnCl₄, CsCuCl₃, and K₂FeCl₅,

(4) sodium bromide or ammonium chloride, and

(5) transition metal halides, including zinc chloride.

Other complex compounds can be found in U.S. Pat. No. 4,848,994 issuedon Jul. 18, 1989 and incorporated by reference herein for all purposes.

As described below, the system may be configured by an electroniccontroller to provide a burst discharge for cooling a device or productin a very short period of time. In one embodiment, each absorptionperiod, which provides the burst cooling of the complex compound may bebetween 5 seconds and 300 seconds. Food process cooling is typical atthe high end of the time range while cooling of heat generating lasersystems, microwaves, etc. can be at the short or high end. In otherembodiments, the absorption period may be between 10-200, 15-150,20-100, 30-75 or 40-50 seconds. In other embodiments, the absorptionperiod may be less than 200, 175, 150, 125, 100, 75, 50, 25, 10, 15, 7,or 5 seconds long. The absorption period may also be divided intomultiple “pulse periods”. For example, one absorption period of 25seconds may be made up of three pulses of absorption for five secondseach, with a five second rest between each pulse. Other numbers ofpulses within the absorption period, or number of rest periods are alsocontemplated. For example, the number of pulses within an absorptionperiod may be 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or morepulses per absorption period. The pulse periods may be between 5-10,5-20 or 5-30 seconds long each in some embodiments.

The controller may be configured in many ways to activate a burst modecooling cycle. In one embodiment, the controller is any electronicdevice or apparatus that activates, modulates, or deactivates the flowof refrigerant or heat transfer fluids in the system. The controller mayalso be any electronic device or apparatus that controls heat at aburner within the system. In one embodiment, the controller is linked toa temperature sensor and activates a burst mode cooling cycle when thetemperature sensor reaches a predetermined target temperature. Thetemperature sensor may be thermally linked to the thermal load beingcooled to that when the thermal load reaches the predetermined targettemperature, a cooling cycle is begun. Alternatively, the controller maybe electronically linked to an activation signal that triggers a burstmode cooling cycle. The activation signal may be controlled by apredictive process that senses a variety of data and then predicts whento activated a cooling cycle. For example, the controller may sense thepresent temperature of the thermal load, the time since the lastactivation, and the state of other equipment of devices linked to thethermal load. Using this data, the system may activate a burst modecooling cycle just before the thermal load starts to heat. For example,if the thermal load is a flash freezing system, the controller maydetect when the system may need to begin freezing food or otherproducts. Just prior to the freezing cycle being needed, the systeminitiates a burst of cooling so that the thermal load is cooled at theappropriate time. In some embodiments, the controller may activate acooling cycle 1, 2, 3, 4, 5, 6, or 10 seconds in advance of a determinedcooling event.

Using the lean end of the coordination sphere yields faster rates ofabsorption with the option of pulsing within each absorption periodresulting in even faster burst reaction rates. As used herein thecoordination sphere is a central metal ion and its coordination ligands,in the subject coordination sphere, but not counting ligand molecules ofa possible lower coordination sphere. In one embodiment the lean end ofthe coordination sphere is the lower 50% of the subject coordinationsphere where less than 50% of the possible coordinating ligands, such asammonia, are bound to the central metal ion. In other embodiments, thelean end of the subject coordination sphere may be the lower 30%, 25% or20% of the coordination sphere. For example, the highest rates ofammonia absorption are when the complex compounds in the sorber have themost absorption sites available for bonding to ammonia molecules. SrCl₂has eight available absorption sites for ammonia. The first coordinationsphere is the 0-1 sphere, the second is the 1-8 sphere, the latter beingof interest in the majority of embodiments of to the subject matter ofthis disclosure. The 0-1 and 1-8 spheres are the theoretical numbers notaccounting for solid-solid solution effects that narrow the window ofthermodynamic monovariancy. In the case of SrCl₂, the effective range ofmonovariancy in which the vapor pressure is independent of the ligandconcentration is about 1.8-7.5. Thus, the time required for a mole ofSrCl₂ to go from 1.8 mole of absorbed ammonia to 2.8 moles of ammonia inthat second coordination sphere is much shorter than for one mole ofSrCl₂ to go from 2.8 moles of absorbed ammonia to 3.8 moles of absorbedammonia. However, in certain lower temperature ambient conditions,particularly less than 20° C., it may be preferable to start with lessthan 1.8 moles of ligand, and start the absorption within the 0-1sphere, the first coordination sphere. For SrCl₂, the lean end of thecoordination sphere may be the lower 20% of the coordination sphere.This is similar for the majority of other compounds. Embodiments of theburst mode cooling system described herein are tuned to keep the complexcompounds in the sorber at their leanest, with the fewest number ofmoles of ammonia, in order to allow higher reaction rates and resultingshorter reaction times for each absorption reaction, thus providinghigher cooling power.

In one embodiment, the system is designed to absorb ammonia in the“leanest” portion of each complex compound's absorption profile. Thus,in embodiments of this system, if SrCl₂ is the compound, and each moleof SrCl₂ is capable of absorbing eight moles of ammonia, the system willbe configured to have an absorption cycle that preferably absorbsammonia when 3.5 or three or less moles of ammonia are absorbed to eachmole of SrCl₂. If more than three moles of ammonia are absorbed ontoeach mole of SrCl₂ then the controller may instruct the system toperform a sorber heating cycle to drive off the bound ammonia and resetthe complex sorbent to be back into its preferred range of fewer thanthree moles of ammonia per mole of SrCl₂ for another round of burst modecooling.

Similarly, if MnCl₂ is the sorbent and can absorb up to six molecules ofammonia for each molecule of MnCl₂ with the relevant coordination spherebeing the 2-6 mole sphere, then the system will be configured to have anabsorption cycle to preferably absorb ammonia only when each mole ofMnCl₂ has about 3.5, 3 or fewer moles of absorbed ammonia molecules,absorbing from about 2 moles of ammonia per mole of MnCl₂ to 3.5 molesof ammonia per mole of MnCl₂.

If CaBr₂ is the sorbent then the system may be configured to have anabsorption cycle wherein ammonia is absorbed onto the CaBr₂ sorbent whenless than about 3.5 moles of ammonia are already bound, absorbing fromabout 2 moles of ammonia per mole of CaBr₂ to 3.5 moles of ammonia permole of CaBr₂. In some embodiments, the system may be configured to onlyabsorb ammonia onto a CaBr₂ sorbent when there are less than about 3moles of ammonia already bound to the CaBr₂ sorbent. Theseconfigurations can be managed by using the controller to tune theadsorption and desorption times to be active when the compound can beloaded with ammonia most efficiently.

In one embodiment, the temperature change/desorption period may bebetween about 180 seconds and about 15 minutes in order to reload thesystem. In some embodiments, the desorption period is less than about 5,4, or 3 minutes, or less.

FIG. 1 shows the results of an experiment wherein the rate(mole/mole/hr) of ammonia bonding to a CoCl₂ sorbent in a heat exchangerwas measured over time at a pressure of 0.030 Bar and a constanttemperature of 45° C. It was found that the rate of ammonia absorptionwas much faster during the initial reaction when CoCl₂ was at the leanend of the coordination sphere and few moles of ammonia were bound toeach mole of CoCl₂. As shown, after about the first four minutes ofabsorption the rate reached over 14.5 moles of ammonia being added toeach mole of CoCl₂ per hour. However, after the first about fourminutes, the rate of ammonia addition started to decrease as ammoniabonding positions on each mole of CoCl₂ were taken up by earlierreactions. Higher differential temperatures and pressures yield muchhigher rates, but the ratio of reaction rates between the lean and richend of the coordination sphere either remains the same or gets even morepronounced.

FIG. 2 shows the results of an experiment wherein the rate(mole/mole/hr) of ammonia bonding to a SrCl₂ sorbent in a heat exchangerwas measured over time at a pressure of 2.396 Bar and a constanttemperature of 45° C. It was found that the rate of ammonia absorptionwas much faster during the initial reaction when SrCl₂ was at the leanend of the coordination sphere and few moles of ammonia were bound toeach mole of SrCl₂. As shown, after about the first six minutes ofabsorption the rate reached over 17 moles of ammonia being added to eachmole of SrCl₂ per hour. However, after the first about six minutes, therate of ammonia addition started to decrease as ammonia bondingpositions on each mole of SrCl₂ were taken up by earlier reactions. Asis the case with all complex compounds of this material class, higherdifferential temperatures and pressures yield much higher rates, but theratio of reaction rates between the lean and rich end of thecoordination sphere either remains the same or becomes even morepronounced.

Optimum reaction rates for embodiments are also dependent on a number ofindependent parameters including adsorbent density, the mass diffusionpath length, the heat or thermal diffusion path length, as well as thethermodynamic operating conditions. The latter include the overallprocess conditions i.e., the specific temperature and pressureconditions in which the process is carried out, the differentialpressure or i.e., the difference between the operating or systempressure and the equilibrium pressure of the complex compound, and theapproach temperature or ΔT. One consequence of performing adsorption anddesorption reactions at relatively fast speeds to provide burst coolingis that the approach temperature may be higher than normal. Inembodiments of the invention, the approach temperature may be from 15° Kand 35° K to cause a faster desorption of the ammonia.

In one embodiment, when the reactor is configured with an approachtemperature for desorption of the ammonia at relatively hightemperatures of 15° K and 30° K, the system may stop heating prior tothe end of the desorption cycle. For example, the controller mayinstruct the system to stop heating the desorber 2, 3, 4, 5, 10, 20, 30or more seconds before the desorption reaction is ending. This allowsthe ammonia to continue to desorb from the complex compound, but alsoallows the desorber to being cooled in order to get ready for the nextround of absorption. The embodiment allows the desorber to begin coolingin advance of the next refrigeration cycle in the system and provides ahigher overall efficiency in cycling the sorber for the next round ofburst mode cooling.

In one embodiment the sorber is also configured to stop being cooled inadvance of the end of the absorption cycle in order to prepare thesorber for the next cycle of heat. For example, the controller may stopcirculating cooling fluid to the sorber 2, 3, 4, 5, 10, 20, 30 or moreseconds before the reaction is ending. In one embodiment, the coolingloop of the system often comprises glycol and water or other suitableheat transfer fluids that may be turned off in order to allow theabsorber rise in temperature before the next reaction cycle begins. Inother embodiments, the cooling loop may use ammonia or other phasechange fluid to cool the sorber.

Generally, the reactor should be designed to have a relatively lowthermal mass. A reactor with more thermal mass takes longer to heat upand cool down. Embodiments of this invention include reactors that canprovide efficient bursts of cooling, which means that the ability torapidly heat and cool are one consideration of the reactor design. Oneway to measure the thermal mass is the ratio of the total weight inkilograms of the reactor (including shell, fins, complex compounds,etc.) to the weight in kilograms of the complex compounds (salt) withinthe reactor. In one embodiment, this ratio is less than 7:1 and morepreferably less than 6:1, 5:1, 4:1 or 3:1. In one embodiment, thethermal mass of the reactor is reduced by manufacturing portions of thereactor out of advanced materials such as aluminum, titanium, advancedfiber composites, or other similar light-weight materials.

Embodiments may be part of a system configured to cool devices such asdirected energy weapons systems, such as laser, electro-laser andmicrowave systems which rapidly heat when activated. Embodiments couldalso be part of rapid freezing systems for any industry such as the foodand beverage industries.

FIG. 3 shows one exemplary burst mode cooling system 100 that has acomplex compound based sorber 110 that is designed to absorb and desorbammonia. Additional details on the sorber 110 can be found withreference to FIG. 4 below. The cycle begins when a burst cooling valve116 is opened under control of an electronic controller 118. Opening thevalve 116 allows condensed ammonia stored in an ammonia reservoir 120 torapidly expand through an expansion valve 124 and move through anevaporator 128. As the expanding ammonia liquid changes to a gas andmoves through the evaporator 128 it absorbs heat from an adjacentthermal load 130. This rapidly cools the thermal load 130. The ammonialiquid that was evaporated to gas by the thermal load 130 moves throughthe open burst cooling valve and into an inlet/outlet 131 to the sorber110 where it becomes absorbed onto the complex compounds within thesorber 110.

After the burst cooling is completed, the system needs to drive theabsorbed ammonia gas from the complex compounds and so activates aheating pump 134 that can circulate heated thermal media, such as anethylene glycol and water mixture into the sorber. In one embodiment,the thermal media is approximately 30% ethylene glycol in water,however, other compositions of thermal media are also within the scopeof embodiments of this invention. For example, the thermal media may beSYLTHERM™ (Dow Corning Corporation, Midland, Mich.), PARATHERM™(Paratherm, King of Prussia, Pa.) or similar heat transfer fluids.

Activating the heating pump 134 moves the thermal media into a burner136 that heats the media to a target temperature. In one embodiment thetarget temperature is between 125° C. and 140° C. In another embodimentthe target temperature is 130° C. The heated thermal media is thenpumped through a control valve 138 and into a hot thermal media inlet140 within the sorber 110. The thermal media flows out of the sorber 110from a hot thermal media outlet 144 and back to the heating pump 134.The heated thermal media circulates through the sorber 110 for apredetermined period of time to drive off the absorbed ammonia gas sothat the sorber can enter another cycle of absorbing ammonia onto itscomplex compound surface.

To run the heated thermal media efficiently through the sorber 110, thesystem also includes a heat exchanger 148 that can have heated thermalmedia flowing through it during times when the sorber 110 does not needto be heated. The control valve 138 is controlled by the controller toswitch the flow of thermal media to the heat exchanger 148 when thesorber does not need to be heated, and to the sorber 110 when it's timeto heat the sorber within the refrigeration cycle.

The heated ammonia gas moves out the inlet/outlet 131, through anammonia gas return valve 132, and flows towards a condenser 119 to startan additional cycle. The controller 118 controls the burst cooling valve116 and the ammonia gas return valve 132 to that ammonia gas enters andexits the sorber properly during each cycle. At the condenser 119, theammonia gas is cooled by a fan 121 and condensed towards a liquid statebefore flowing into an ammonia reservoir 124. The ammonia reservoir actsas a holding container for pressurized ammonia gas or liquid prior tobeing recirculated to the sorber, or used for burst mode cooling.

After the sorber is heated to drive off absorbed ammonia, the sorberneeds to cool to be able to absorb ammonia for the next round in therefrigeration cycle. To help cool the sorber, the system includes acooling pump 152 that circulates ammonia from the ammonia reservoir 120into a series of cooling thermal media lines within the sorber 110. Thecooling pump 152 is activated by the controller 118 and draws ammoniafrom the reservoir 120 flows it into a thermal media inlet 162 and out athermal media outlet 164. The ammonia absorbs heat from inside of thesorber 110 and then recirculates that heated ammonia to the condenser119 to help cool down the sorber for the next round of absorption.

Additional details on the sorber 110 are shown in FIG. 4. The sorber 110includes a lower end 202 and an upper end 213 that is opposite the lowerend 202. The ends 202 and 213 facilitate moving thermal transfer mediathrough a set of heat transfer tubes 220 that traverse the interior ofthe sorber 110. The lower end 202 includes the hot thermal media inlet140 and an outlet 144 that communicate with a first circuit of the heattransfer tubes 120. The upper end 213 includes the cold thermal mediainlet 162 and an outlet 164 that communicate with a second circuit ofthe heat transfer tubes 120. The sorber 110 may include other inletsand/or outlets as needed to move thermal transfer media and/or sorbergas through the system. The various inlets and outlets may providepiping or other channels through which the sorber gas and/or refrigerantmay flow.

The sorber 110 has an outer shell 210 that is an elongated cylindricallayer that surrounds and encapsulates a complex compound sorbent 270disposed within the interior of the sorber 110. In some embodiments, theshell 210 may have other suitable shapes and may be composed of morethan one layer. The shell 210 may be formed from a rigid material suchas a metal or metal alloy, but it may be formed from other suitablematerials as well. Among other things, the shell 210 acts as a barrierfor the sorbent 270 to prevent the sorbent 270 from expanding radiallyoutward when the sorber 110 is pressurized.

The lower end 202 of the sorber 110 includes a hot water box 230 and afeed box 240. In some embodiments, the hot water box 230 is a fluidbonnet. The hot water box 230 contains a fluid, such as ethyleneglycol/water that is then distributed by the feed box 440 through theheat transfer pipes 220 which run adjacent the complex compound sorbentand are used to heat the sorbent to release the ammonia gas.

Similarly, the upper end 213 of the sorber 110 includes a cold box 232.The cold box 232 may be a cooling fluid bonnet. The cold box 232provides cool fluid, such as ammonia from the reservoir 120 to a secondcircuit of heat transfer tubes 120 within the sorber 110 to cool thesorber 110 between refrigeration cycles.

By flowing a heat transfer medium 120 through the heat transfer pipes220, which are adjacent the complex compound material, heat may betransferred to and from the sorbent material. The heat transfer pipes220 may have bends 222, which may be “U” shaped bends. The bends 222 maybe located on either or both of the ends 202, 213 of the sorber 110. Insome embodiments, the bends 222 are U-shaped and located near the upperend 213 of the sorber 110. Therefore, in some embodiments the sorber hasa dual bonnet design with two circuits for heating and cooling thesorbent material within the sorber 110.

The sorber 110 includes a sorber gas pipe 245 for flowing the sorber gasto and from the sorber 110. The sorber gas flows from the pipe 245 andinto the sorber 110 in various locations. In some embodiments, there mayonly be one location. As shown, the pipe 245 connects with the sorber110 at three locations along the side of the sorber 110. The pipe 245may also connect with the sorber 110 in other locations. The sorber gasflows from the pipe 245 and into a set of porous gas distribution tubes250. In some embodiments, sorber gas flows from the pipe 245 and intocompartments (not shown) in the sorber 110 and then into the gasdistribution tubes 250. A variety of configurations are possible, andthese are just some examples. One embodiment of a sorber can be found inU.S. Patent Publication 2016/0238286 A1 published on Aug. 18, 2016 andincorporated herein by reference for all purposes.

FIG. 5 shows an illustration of the controller 118, which is programmedwith instructions to control operations of the system 100. Thecontroller 118 includes a processor 310 which may be any type ofwell-known microprocessor or microcontroller that is capable of managingthe valves, fans and other components of the system 100. The processor310 is connected to a Burst Mode Module 315 which includes instructionsfor activating a burst of cooling to the thermal mode under certainpredetermined conditions. In one embodiment, the Burst Mode Module 315is programmed to activate the burst cooling valve 116 to rapidly coolthe thermal load 130 when a predetermined signal is received bycontroller 118. The signal may be an activation signal from a systemconnected to the thermal load. For example, if the thermal load is apiece of machinery or equipment, it may send a signal to active theburst mode cooling just prior to the machinery or equipment starting arapid heating cycle. In one embodiment the machinery or equipment may beweapons or other equipment that rapidly heats upon activation. In oneembodiment the weapon may be a laser or microwave type weapon that heatsin relatively short bursts as the weapon is discharged. With eachdischarge the weapon system may trigger the burst cooling mode of thesystem 100 in order to reduce the temperature of the weapon system. Inanother embodiment, the machinery or equipment may be configured toabsorb heat from a mechanical or electrical system that rapidly heatswhen activated. That mechanical or electrical system may be programmedto trigger the burst mode cooling whenever bursts of energy are usedwithin the mechanical or electrical system so that additional cooling ofspecific components is warranted.

The controller 118 also includes a sorber cooling module 320 thatcontrols cooling of the sorber after the sorber has been heated to drivethe absorbed ammonia from the complex compound sorbent. The sorbercooling module 320 may work in conjunction with the ammonia gas returnvalve 132 which helps circulate cool ammonia vapor/liquid through thesorber 110 to cool the sorber to a target temperature before initiatinga burst mode cooling cycle.

The controller 118 also has a load temperature module which monitors thetemperature of the thermal load 130 attached to the evaporator 128. Inone embodiment, the load temperature module 325 activates a burstcooling mode when the temperature of the thermal load 130 reaches apredetermined load temperature. For example, when the temperature of thethermal load is above 10° C. and below 50° C., then the load temperaturemodule activates the burst cooling valve to cool the thermal load belowits target temperature. In other embodiments, the burst cooling valvemay be activated when the temperature of the thermal load is above 15°C. and below 45° C. or above 20° C. and below 40° C. Of course,embodiments are not limited to performing only a single burst coolingprocedure. During activation, the thermal load, or an attached weaponssystem, may request multiple burst mode cooling operations to maintainthe temperature of the thermal load below a certain target temperature.

In one embodiment the controller may manage the variable speed operationof various pumps and fans within the system based on the temperature ofthe thermal load. For example, as the temperature of the thermal load,or surrounding environment, increases the speed of pumps and fans withinthe system may also increase. Similarly, as the temperature of thethermal load, or surrounding environment decreases, the controller mayslow the speed of the pumps and/or fans.

The controller may also include a sorber heating module 340 which isconfigured to heat the sorber 110 at the proper time in the coolingcycle to drive the ammonia from the complex compound sorbent. Thecontroller may be connected to the valve 138 which determines if theheated liquid flowing through the burner 136 is directed into the sorber110 or instead to the heat exchanger 148. When the sorber heating module340 determines that its time to drive off the ammonia gas it can openthe valve 138 which allows a heated aqueous mixture to flow through thesorber and heat the sorbent material.

Each of the instructions may be stored in a memory 330 that is connectedto the processor 310 within the controller 118.

FIG. 6 is a flow diagram of a process 400 for performing a burst modecooling of a thermal load. The process 400 begins at a start state 402and then moves to a decision state 404 wherein a determination is madewhether a cooling event has been detected. A cooling event may be, forexample, the determination that the thermal load has reached a targettemperature. Another cooling event may be, for example, the receipt of asignal from a machine or equipment attached to the thermal load that itwill require burst cooling at an upcoming time. If a determination ismade at the decision state 404 that no cooling event has been detected,the process 400 moves to a state 406 where the system enters amaintenance mode where the cooling system can prepare for a next coolingevent. For example, the system may use the maintenance mode to drive offammonia bound to the sorbent from a prior burst cooling event. Thesystem may also start to circulate some of the ammonia from the ammoniareservoir through cooling pipes within the sorber to reduce thetemperature of the sorber so it can be prepared for an additional burstcooling procedure. The system may perform other measures within thesorber or system to prepare for a future burst mode cooling procedure.Once the maintenance mode is complete at the state 406, the process 400returns to the decision state 404 to wait until a cooling event isdetected.

If a cooling event is detected at the decision state 404, the process400 moves to a state 408 wherein the type of required cooling isidentified. For example, the system may activate longer or shorterbursts of cooling depending on the type of cooling required by thetarget load or other machine or equipment. Once the type of cooling isidentified at the state 408 the process 400 moves to a state 412 whereinthe cooling parameters are determined. The cooling parameters may be thenumber of burst modes to activate, the over length of the coolingrequired or any other parameter necessary for the system to properlycool the thermal load.

The process 400 then moves to a state 418 wherein the burst cooling isactivated by opening the burst cooling valve 116 according to thedetermined cooling parameters. After the burst cooling has completed theprocess 400 moves to a state 420 wherein the sorber is recharged byheating the sorbent to drive off the ammonia that has bound at the priorstate. The process 400 then moves to a decision state 424 to determineif the cooling process is completed, and if not then the process 400returns to the decision state 404 wherein the process 400 waits todetect another cooling event. If the overall process is complete at thedecision state 424, then the process terminates at an end state 450.

Headings are included herein for reference and to aid in locatingvarious sections. These headings are not intended to limit the scope ofthe concepts described with respect thereto. Such concepts may haveapplicability throughout the entire specification.

The previous description of the disclosed implementations is provided toenable any person skilled in the art to make or use the presentinvention. Various modifications to these implementations will bereadily apparent to those skilled in the art, and the generic principlesdefined herein may be applied to other implementations without departingfrom the spirit or scope of the invention. Thus, the present inventionis not intended to be limited to the implementations shown herein but isto be accorded the widest scope consistent with the principles and novelfeatures disclosed herein.

While the above description has pointed out novel features of theinvention as applied to various embodiments, the skilled person willunderstand that various omissions, substitutions, and changes in theform and details of the device or process illustrated may be madewithout departing from the scope of the invention.

1. A burst mode ammonia based cooling system, comprising: at least onesorber comprising a complex compound sorbent configured to absorb anddesorb ammonia; at least one heat source thermally connected to the atleast one sorber; one or more condensers in fluid communication with theat least one sorber; one or more an evaporators in fluid communicationwith the at least one sorber; and a burst mode controller configured toactivate a valve to provide a burst of heat absorption at theevaporator, where the absorption period of the complex compound isbetween 5 seconds and 300 seconds and the desorption period is between180 seconds and 15 minutes.
 2. The system of claim 1, wherein thesorbent is one of SrCl₂, CaBr₂ and MnCl₂.
 3. The system of claim 1,wherein the controller is configured to control absorption of ammonia atthe lean end of a coordination sphere for the complex compound sorbent.4. The system of claim 3, wherein the lean end of the coordinationsphere is the lower 50% of the coordination sphere.
 5. The system ofclaim 3, wherein the lean end of the coordination sphere is the lower30% of the coordination sphere.
 6. The system of claim 3, wherein thecontroller is configured to control the absorption of ammonia to a SrCl₂sorbent when three or less moles of ammonia are absorbed to each mole ofSrCl₂.
 7. The system of claim 3, wherein the controller is configured tocontrol the absorption of ammonia to a SrCl₂ sorbent when 3.5 or lessmoles of ammonia are absorbed to each mole of SrCl₂.
 8. The system ofclaim 7, wherein the lean end of the coordination sphere for the SrCl₂sorbent is the lower 20% of the coordination sphere.
 9. The system ofclaim 3, wherein the controller is configured to control the absorptionof ammonia to a CaBr₂ sorbent when three or less moles of ammonia areabsorbed to each mole of CaBr₂.
 10. The system of claim 3, wherein thecontroller is configured to control the absorption of ammonia to a CaBr₂sorbent when 3.5 or less moles of ammonia are absorbed to each mole ofCaBr₂.
 11. The system of claim 3, wherein the controller is configuredto control the absorption of ammonia to a MnCl₂ sorbent when three orless moles of ammonia are absorbed to each mole of MnCl₂.
 12. The systemof claim 3, wherein the controller is configured to control theabsorption of ammonia to a MnCl₂ sorbent when 3.5 or less moles ofammonia are absorbed to each mole of MnCl₂.
 13. The system of claim 1,wherein the absorption period is divided into a plurality of pulseperiods.
 14. The system of claim 13, wherein the plurality of pulseperiods are between 5 and 30 second long each.
 15. The system of claim13, wherein the absorption period is 30 seconds, which is made up ofthree pulse periods of absorption for five seconds each, with a fivesecond rest between each pulse period.
 16. The system of claim 1,wherein the thermal mass of the system is less than 7:1, which is theratio of the total mass (kilograms) of the reactor to the total mass(kilograms) of the complex compound sorbent.
 17. The system of claim 1,wherein the sorber comprises a plurality of porous gas distributiontubes for distributing the ammonia to the complex compound sorbent. 18.The system of claim 1, wherein the evaporator is configured to mate witha thermal load from a product or device.
 19. The system of claim 18,wherein the thermal load is part of a flash freezing device or product.20. The system of claim 18, wherein the thermal load is part of adirected energy weapons system.
 21. The system of claim 1, wherein thecontroller is linked to a temperature sensor and activates a burst modecooling cycle when the temperature sensor reaches a predetermined targettemperature.
 22. The system of claim 1, wherein the controller is linkedto an activation signal, that triggers a burst mode cooling cycle. 23.The system of claim 22, wherein the activation signal is activated by apredictive process that determines when to activate a burst mode coolingcycle.
 24. The system of claim 1, wherein the at least one sorbercomprises three sorbers.
 25. A method in a complex compound sorbersystem of burst mode cooling a thermal load, comprising: detecting whento activate a burst mode cooling cycle; activating a valve that allowsammonia to flow into at least one sorber comprising a complex compoundsorbent, wherein the sorber is connected to an evaporator and theactivation provides a burst of heat absorption at the evaporator; andcontrolling the absorption period of the complex compound to between 5seconds and 300 seconds and the desorption period to between 180 secondsand 15 minutes.
 26. The method of claim 25, wherein the at least onesorber comprises a complex compound sorbent that is one of SrCl₂, CaBr₂and MnCl₂.
 27. The method of claim 25, wherein controlling theabsorption period comprises controlling the absorption of ammonia so itbinds to the complex compound sorbent at the lean end of a coordinationsphere.
 28. The method of claim 27, wherein the sorbent comprises SrCl₂and the lean end of the coordination sphere for the SrCl₂ sorbent is thelower 20% of the coordination sphere.
 29. The method of claim 27,wherein controlling the absorption period comprises controlling theabsorption of ammonia to a SrCl₂ sorbent when three or less moles ofammonia molecules are absorbed to each mole of SrCl₂.
 30. The method ofclaim 27, wherein controlling the absorption period comprisescontrolling the absorption of ammonia to a SrCl₂ sorbent when 3.5 orless moles of ammonia molecules are absorbed to each mole of SrCl₂. 31.The method of claim 27, wherein the lean end of the coordination sphereis the lower 50% of the coordination sphere.
 32. The method of claim 27,wherein the lean end of the coordination sphere is the lower 30% of thecoordination sphere.
 33. The method of claim 27, wherein controlling theabsorption period comprises controlling the absorption of ammonia to aCaBr₂ sorbent when three or less moles of ammonia molecules are absorbedto each mole of CaBr₂.
 34. The method of claim 27, wherein controllingthe absorption period comprises controlling the absorption of ammonia toa CaBr₂ sorbent when 3.5 or less moles of ammonia molecules are absorbedto each mole of CaBr₂.
 35. The method of claim 27, wherein controllingthe absorption period comprises controlling the absorption of ammonia toa MnCl₂ sorbent when three or less moles of ammonia molecules areabsorbed to each mole of MnCl₂.
 36. The method of claim 27, whereincontrolling the absorption period comprises controlling the absorptionof ammonia to a MnCl₂ sorbent when 3.5 or less moles of ammoniamolecules are absorbed to each mole of MnCl₂.